Abstract: Methods and devices for producing chemical arrays are provided. Aspects of methods include employing a dedicated wash fluid reaction chamber. In certain embodiments, aspects include contacting a surface with at least a deblocking reagent to produce a deblocked surface, washing the deblocked surface in a dedicated wash fluid reaction chamber, e.g., flow cell, and then contacting the washed surface with one or more reactive moieties in a spatially controlled manner. Also provided are devices configured for use in practicing the subject methods.